- at least one epoxy functional group, and
- at least one R¹group wherein R¹is a vinyl functional (CH₂═CH—) group or at least one —Si(R²)₃functional group and wherein R²═hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations thereof

As already said, in the support according to the present invention, the hydroxyl and/or primary-secondary amino functional groups of the water-soluble polymer have been functionalized beforehand with at least one organic compound.

In a preferred embodiment, the epoxy functional group of said organic compound corresponds to a saturated three-membered cyclic ether.

The term cellulose fibre-based support is understood to mean a support that contains cellulose fibres that have been more or less adapted in proportions ranging from 50 to 99% by weight for purposes of their desired characteristics (density, transparency, mechanical properties).

The term synthetic fibre-based support, commonly called nonwoven, is understood to mean as a sheet or web structures bonded together by entangling fibre or filaments by a mechanical, thermal or chemical process. Nonwovens are flat, porous sheets that are made directly from separate fibres (wetlaid process) or from molten plastic particles (spundbound, meltblown or electrospinning processes). Typical fibres used in the production of nonwovens are made of: polyester (for example: polyethylene terephthalate, polybutylene terephthalate, polylactic acid), polyolefines (for example: polypropylene, polyethylene), polyamides (for example: nylon 6, 6-6, 12, 6-12), polyphenylene sulfide, polycarbonate, viscose and fibreglass.

Substrates of cellulosic and synthetic fibres can be produced and adapted in relative proportions ranging from 1 to 99% by weight for purposes of their desired characteristics. For instance, some applications may involve or require the addition of small amounts of synthetic fibres to the cellulose as a reinforcement material.

In a particular embodiment, the support is a cellulose fibre-based support.

The coating layer that contains the functionalized water soluble polymer is designed to afford silicone barrier properties to the surface of the fibre-based support.

When the water soluble polymer contains hydroxyl functional groups, the linkage between the polymer and the organic molecule is made through an ether bond with a hydroxyl functionality in position 2 (i.e.: 2-hydroxyether) (as inFIG. 1).

When the water soluble polymer contains primary or secondary amino functional groups, the linkage between the polymer and the organic molecule is an alkylated amine (secondary or tertiary amine) with a hydroxyl function in position 2 (i.e.: 2-hydroxyamine) (as inFIG. 2). In a particular embodiment, the water soluble polymer may comprise both hydroxyl and primary-secondary amino functional groups (i.e.: chitosan).

In both cases (OH and NH/NH₂containing polymers), the chemical reaction involved is an alkylation reaction where no other by-products are produced during the reaction (i.e.: water is not produced).

Additionaly, the coating layer comprising the water-soluble polymer may contain at least one functionalized water-soluble polymer and at least one water soluble polymer that has not been functionalized. As a result, functionalized and unfunctionalized hydroxyl or amino functional groups may be contained in the same water-soluble polymer, or they may be contained in a mixture of a least two water-soluble polymers comprising different hydroxyl or amino functional groups.

Furthermore, the coating layer that contains the functionalized water-soluble polymer may also contain other water-soluble binders, conventional additives, pigments and latexes. Depending on the nature of the water soluble polymer, a suitable crosslinker can be advantageously added in the formulation in order to render the polymer water insoluble after the application of the polymer on the substrate and the drying of the product. In fact, once the coated support is dried, the water soluble polymer can become water insoluble due to its cross-linking. The skilled man in the art knows that the hydrosoluble properties of a polymer can be affected when a crosslinker is added.

Interestingly, when the organic molecule is not water soluble, the grafting reaction can still occur in water. In fact, by vigorous stirring, it is possible to create an emulsion of the organic molecule in the water solution and the grafting reaction occurs even if the polymer and the reactant are not in the same phase.

In a preferred embodiment of the invention, the water-soluble polymer containing hydroxyl functional groups can advantageously be chosen from the group comprising natural and modified polysaccharides such as starch; CMC (carboxymethyl cellulose); alginate; chitosan, pectine, chtin, glycogen, arabinoxylane, cellulose and synthetic polymers such as poly(vinyl alcohol); hydrolysed or partially hydrolysed copolymers of vinyl acetate, which may be obtained for example by hydrolysing ethylene—vinyl acetate (EVA) or vinyl chloride—vinyl acetate, N-vinyl pyrrolidone—vinyl acetate, and maleic anhydride—vinyl acetate copolymers.

In a preferred embodiment, the water-soluble polymer containing hydroxyl functional groups is advantageously starch.

In another preferred embodiment, the water-soluble polymer containing hydroxyl functional groups is advantageously PVA.

In a preferred embodiment of the invention, the water-soluble polymer containing primary-secondary amino functional groups can advantageously be chosen from the group comprising polyethyleneimine; polyallylamine; chitosan; polyacrylamide; partially or totally hydrolized polyacrylamide; parlially or totally hydrolized polyvinylamine, polyamines based on amino-ethyl-piperazine; and in general big molecules containing aliphatic or aromatic polyamino functional groups as for example spermidine, spermine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine. This water-soluble polymer containing amino functionalities is advantageously polyethyleneimine, polyallylamine and parlially or totally hydrolized polyvinylamine.

Typically, the water soluble polymers that are grafted correspond to a molecule containing at least one element from the group of C, H, N, O, non-metals such as the halogens, Si, S, P, metals such as Na, Li, K, Mg, Pb, etc.

The molecular weight of the water soluble polymer comprising primary-secondary amino or hydroxyl functional groups preferably ranges from 1,000 to 1,000,000 a.m.u, advantageously from 50,000 to 150,000 a.m.u.

As already stated, the organic molecule enabling the grafting of the water soluble polymers contains at least one epoxy functionality (—CH—O—CH₂) as well as at least one functional group among vinylic (—CH═CH₂), silicone hydride (Si—H), and silanol (Si—OH) groups. The epoxy group enables the organic molecule to be grafted onto the water-soluble polymer containing hydroxyl or primary-secondary amino functions by an alkylation reaction.

In the grafting reaction reported in the present invention, the organic molecule can contain, in addition to the epoxy functional group, silanol groups (Si—OH) that are able to react with silicone after siliconizing. It is familiar to one skilled in the art that the silanol functionality can be formed from the hydrolysis of alkoxylated silanols (Si—O—R*, where R* can be a methyl, ethyl, propyl, isopropyl, butyl, isobutyl etc. functyonality). The reaction concerns hydrolysis of alkoxylated silanols in water;

which can be catalysed in acid or basic pH. This reaction leads to the formation of by products such as alcohols (methanol, ethanol, propanol, isopropanol, butanol, isobutanol etc.). Organic molecules comrprising silanol groups resulting from the in situ hydrolysis of alkoxylated silanol groups (Si—OR*) exhibit the same reactivity as organic molecules comprising silanol groups (Si—OH) that therefore do not require any in situ hydrolysis. However, over time, alkoxylated silanols are more stable than silanols, and therefore provide a more convenient raw material reactant for the grafting reaction of the water soluble polymer.

With regards to the polymer grafting reaction involving an alkylation, carrying out the reaction in basic or acidic condictions can catalyze the alkylation. In fact, aqueous acidic conditions can enhance the activatation of the oxygen atom of the epoxy group while basic conditions can enhance the activatation of the nucleophile that reacts with the epoxy group. Basic pH conditions are usually preferred to the acid conditions since it decreases the eventual formation of side-products (such as dialcohols resulting from the reaction of the epoxy group with water and subsequent inactivation of the organic molecule for the grafting reaction). Moreover, basic pH conditions are preferred due to the nature of some base polymers, such as polysaccharides, which are more stable in basic conditions compared to acid conditions. In fact, in acid pH conditions, polysaccharides can undergo hydrolysis reaction and therefore exhibit different polymer properties, or be definitely damaged.

After the grafting reaction of the water soluble polymer with the organic molecule, such a functionalized water soluble polymer can then be coated onto the fibre-based support using any kind of surface treatment from the coating technology. The coating layer is layed down onto the fibre-based support, thereby producing, in a single and rapid step on the industrial machine, a support exhibiting the desired functionality and a barrier between the silicone and the support.

Therefore, the product produced by the described process presents at the web surface vinylic or silicone hydride or silanol functionalities which enable a better anchorage of the silicone during the subsequent siliconizing step.

For the sake of simplicity, the water-soluble polymer containing hydroxyl or primary-secondary amino functionalities will be referred to by the abbreviation “PH” in the following. The terms “functionalized PH” will be used to denote the products of the reaction between PH and the organic molecule described in the preceding.

The formula of the organic molecule selected to functionalize the water-soluble polymer containing hydroxyl or primary-secondary amino functionalities is advantageously one of the following:

H₂C—O—CH—(R)—CH═CH₂

H₂C—O—CH—(R)—Si—(R²)₃

wherein R=linear, branched and/or cyclic carbon —(C)_x— chain or a polydimethylsiloxane chain (—O—Si(CH₃)₂—)_yor the combination of the two (—C—)_z—(—O—Si(CH₃)₂—)_jchains that may also contains heteroatoms (X) as part of the chain structure —C—X—C— or as side group of the chain structure —C(X)—;

and wherein R²=hydroxyl (—OH); hydrogen atom (H); alkyl; alkoxy such as for example methoxy (—O—CH₃), ethoxy (—O—CH₂—CH₃), propyoxy (—O—CH₂—CH₂—CH₃)); and combinations thereof.

In a preferred embodiment, x is comprised between 1 and 25, and more advantageously between 5 and 12.

In a preferred embodiment, y is comprised between 1 and 15, and more advantageously between 1 and 8.

In a preferred embodiment, z is comprised between 1 and 15, and more advantageously between 1 and 8.

In a preferred embodiment, j is comprised between 1 and 15, and more advantageously between 1 and 8.

In the two formulae above, “C—O—C” represents a saturated three-membered cyclic ether.

In a preferred embodiment, the —Si(R²)₃group can be chosen from the group comprising —Si(OH)₃, —Si(OH)₂(CH₃), —Si(OH)(CH₃)₂, —Si(H)(CH₃)₂, —Si(H)₂(CH₃), —SiH₃, —Si(O R³)₃, —Si(O R³)₂(CH₃), —Si(O R³)(CH₃)₂, wherein R³are groups chosen from —CH₃, —CH₂—CH₃, —(CH₂)₂—CH₃, —CH(CH₃)₂, —(CH₂)₃—CH₃, —CH₂—CH(CH₃)₂, —(CH₂)₄—CH₃, —(CH₂)₂—CH(CH₃)₂, —C₆H₆and combinations thereof

In a preferred embodiment of the invention, the organic molecules used for the grafting reaction of the water soluble polymer can be prefererably one of the following compounds: 2-vinyloxyrane, 1,2-epoxy-4-pentene 1,2-epoxy-5-hexene, 1,2-epoxy-6-heptene, 1,2-epoxy-7-octene, 1,2-epoxy-8-nonene, 1,2-epoxy-9-decene, 1,2-epoxy-10-undecene, 1 -allyloxy-2,3-epoxypropane, 1-allyloxy-3,4-epoxybutane, 1-allyloxy-2,3-epoxypentane, 1-allyloxy-2,3-epoxyhexane, 1-allyloxy-2,3-epoxyheptane, 1-allyloxy-2,3-epoxyoctane, 1-allyloxy-2,3-epoxynonane, 1-allyloxy-2,3-epoxydecane, 1-allyloxy-2,3-epoxyundecane, glycidoxypropyl trimethoxysilane, glycidoxypropyl triethoxysilane, glycidoxypropyl trisiloxane.

Said organic molecule is advantageously 1,2-epoxy-9-decene or 1-allyloxy-2,3-epoxypropane.

In a preferred embodiment, said organic molecule represents between 0.1% and 20% by weight of the weight of the PH, more advantageously between 0.1% and 10% and even more advantageously between 0.1% and 5%. Even more advantageously, the organic molecule represents 1% by weight of the weight of the PH. The control of the grafting rate thus enables the silicone anchorage to be controlled afterwards, and this is assisted by the presence of the vinylic or silicone hydride or silanol functionality.

The functionalized PH preferably accounts for at least 1% by weight of the layer coated onto the cellulose and/or synthetic fibre-based support, advantageously at least 5%, and even more advantageously between 20 and 100%.

The cellulose layer that forms the support according to the invention typically exhibits a weight ranging from 30 to 160 g/m², preferably from 55 to 140 g/m², and most advantageously in the order of 58 g/m². In a particular embodiment, the weight of the support corresponds to the weight of the fibres. At least one surface of this support is coated with the described coating layer in a quantity of 0.2 to 20 g/m², preferably 1 g/m².

The support according to the present invention may be prepared by the following method:

- formation of a cellulose and/or synthetic fibre-based sheet; with or without a parchementizing process.
- functionalization of at least one water soluble polymer comprising hydroxyl or primary-secondary amino functional groups, by grafting at least one organic molecule comprising at least one epoxy group and at least one R¹functional group wherein R¹can be chosen from a vinyl group, or at least one —Si(R²)₃functional group and wherein R²=hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations thereof. Said organic molecule is able to form covalent bonds with the hydroxyl or primary-secondary amino functional groups of the PH.
- coating the cellulose and/or synthetic fibre support, by methods known to one skilled in the art, with at least one functionalized PH; this step will advantageously be carried out at a temperature between 20 and 95° C., preferably between 50 and 70° C.
- calendering or supercalendering the support if required.

In a particular embodiment of the invention, a chloro-hydrin compound can be used as precursor of the organic molecule. Indeed, the chloro-hydrin compound reacts in basic conditions to form an epoxy compound. The water soluble polymer is therefore still grafted with a molecule containing an epoxy functional group. The conversion from the chloro-hydrin functional group to the epoxy group can be carried out before or during the grafting reaction.

Still according to this particular embodiment, an organic molecule comprising an epoxy group can be obtained from a compound containing a chloro-hydrin group, in aqueous alkaline conditions. In fact, the chloro-hydrin easily reacts with water in alkaline conditions. However, it can be converted to epoxy and therefore be “activated” by a pre-chemical reaction. The chloridric acid which is a by-product of this pre-reaction and it can be converted to a salt (for example sodium chloride, thanks to the alkaline conditions obtained by the addition of sodium hydroxide). The organic molecule comprising an epoxy group and obtained from the chloro-hydrin precursor exhibits the same reactivity as an organic molecule comprising an epoxy group that does need to be pre-activated. The chloro-hydrin precursor can be advantageous in that it is more chemically stable over time and it exhibits lower toxicity as compared to epoxy compounds.

According to a preferred method, the PH is functionalized at a temperature between 20 and 95° C., preferably between 80 and 95° C., in aqueous phase, and eventually in the presence of an organic or an inorganic acid or base as catalyst. In fact, adding an organic or an inorganic acid or base may be necessary when the PH is not already acidic or basic.

Coating techniques known to one skilled in the art further include size-press, metering-size-press, foulard coating, rod coating, “Champion” bar coating, “Meyer” bar coating, air-knife coating, gravure coating, scraper blade coating, sliding blade coating, single- and multilayer curtain coating, reverse roll coating, spray coating, atomisation coating, liquid application system (LAS) coating, kiss coating, foam coating, and any surface coating application process.

The present invention relates as well to a cellulose and/or synthetic fibre-based support of which at least one surface is coated with a layer containing at least one water-soluble polymer comprising hydroxyl or primary-secondary amino functional groups, at least some of which have been functionalized beforehand or after the step of coating with at least one organic compound. Said organic compound contains:

- at least one epoxy functional group, and
- at least one R¹group wherein R¹is a vinyl group or at least one Si—(R²)₃functional group and wherein R²=hydrogen atom, hydroxyl, alkoxy, alkyl, and combinations thereof.

Additionaly, the present invention concerns the process associated to this support.

Generally, a cellulose and/or synthetic fibre-based support according to the invention will be treated in a siliconizing step for use in supports, for instance, for self-adhesive labels, adhesive tapes and vegetable parchment for example. It will be siliconized by any of the methods known to one skilled in the art.

In general, the present invention consists in the functionalization of a water soluble polymer containing amino or hydroxyl functional groups with a molecule having an epoxy function by using a water based process, and in applying the functionalized polymer on a cellulose and/or synthetic fibre-based support by a water based coating technique. The present invention is in contrast to the prior art; which consisted in grafting a molecule directly (or dissolved in organic solvents) onto the cellulosic support or in the pre-grafting a molecule on a polymers using reactions in organic solvents and then coating the resulting grafted polymers on the cellulosic substrate.

EXEMPLARY EMBODIMENTS OF THE INVENTION

The invention itself and the advantages that it offers will be explained in greater detail in the following description of exemplary embodiments and with reference to the following figures.

FIG. 1 represents the alkylation reaction, in an aqueous medium at a basic or acid pH, between a water soluble polymer containing hydroxyl functionalities and an organic molecule comprising both an epoxy function and a functional group among, for instance, Si—H, Si—OH, or vinyl. In this particular case, starch is the water soluble polymer containing hydroxyl functionalities while the molecule having an epoxy functionality refers to the general formula: H₂C—O—CH—(R)—R¹.

FIG. 2 represents the alkylation reaction, in an aqueous medium at a basic or acid pH, between a water soluble polymer containing primary and/or secondary amino functionalities and an organic molecule comprising both an epoxy function and a functional group among, for instance, Si—H, Si—OH, or vinyl. In this particular case, polyethyleneimine is the water soluble polymer containing primary and secondary amino functionality while the molecule having an epoxy functionality refers to the general formula: H₂C—O—CH—(R)—R¹.

Examples

Method for Preparing the Glassine According to the Invention:

A sheet consisting of 100% cellulose fibres is prepared by methods known to one skilled in the art. The support used in the examples is the commercial product Silca Classic Yellow 59 g/m²(from Ahlstrom); for the production of the samples described in the examples, the support has not been coated with the standard formulation but with the formulations reported in the examples 1 and 2. In the case of the standard paper, the commercial grade Silca Classic Yellow has been used as such.

Off-line from the industrial machine, the water soluble polymer containing primary-secondary amino or hydroxyl functionalities is functionalized with an organic molecule by using the methods of examples 1 and 2. After the functionalization reaction, the polymer solution can be mixed with other products commonly used in this application (for example: clays, pigments, latexes, polymers and/or additives), diluted with water to the desired solid content and sent to the industrial machine for the coating step.

The mixture containing the functionalized water soluble polymer is then applied to a surface of the support by coating (1 g/m²), preferably by metering-size-press.

The support is then dried, remoisturized, and super-calandered.

Example 1Functionalization Reaction of a Water Soluble Polymer Containing Primary and/or Secondary Amino Functionalities and Preparation of the Coating Pecipe

In the present example, polyethyleneimine is the polymer containing primary and/or secondary amino functionalities since it contains both functionalities on the same polymer structure.

The commercial polyethyleneimine Polymin P (from Basf) is delivered as a water solution with a solid content of 50% w/w. In order to decrease the viscosity of the solution, Polymin P is diluted with water at a solid content of 20%. For the grafting reaction, an amount of 2% w/w of pure 1,2-epoxy-9-decene (from Sigma-Aldrich), compared to the weight of dry Polymin P, is slowly added to the polymer solution under vigorous stirring. The organic molecule 1,2-epoxy-9-decene is a liquid which is not soluble in water, so a vortex is required to create an emulsion of 1,2-epoxy-9-decene in the polymer solution, forming a cloudy solution. Due to the fact that Polymin P in solution already has a pH between 11 and 13, the addition of a base in order to increase the pH to catalyze the reaction is not required. The solution is heated to 90° C. and mainained at this temperature under stirring for one hour. Subsequently, the pH of the solution is neutralized by addition of a water solution of sulphuric acid. Afterwards, 20% w/w of CMC and 5% w/w of glyoxal compared to the weight of Polymin P are added to the solution. The solution is then diluted with water to a final solid content of 8% w/w. Finally, the solution is transfered to the coating apparatus for the coating step. CMC is added in the coating formulation as a viscosity modifier to improve the film forming properties and the water retention of the coating formulation. Glyoxal is added as a cross-linking agent for the coating formulation.

Example 2Functionalization Reaction of a Water Soluble Polymer Containing Hydroxyl Functionalities and Preparation of the Coating Recipe

In the present example, PVA, Celvol 20/99 (Celanese), is the representative polymer containing hydroxyl functionalities. Celvol 20/99 is delivered as a powder. A dispersion of PVA is produced in water by vigorous stirring. It is then heated up to 95° C. in order to completely dissolve PVA in water. A clear solution with a solid content of 12% is obtained. A solution of sodium hydroxide is added to the PVA solution in order to reach a pH value between 11 and 13. For the grafting reaction, an amount of 2.5% w/w of pure 1,2-epoxy-9-decene (from Sigma-Aldrich), compared to the weight of dry Polymin P, is slowly added to the polymer solution under vigorous stirring. The organic molecule 1,2-epoxy-9-decene is a liquid which is not soluble in water, so a vortex is required to create an emulsion of 1,2-epoxy-9-decene in the polymer solution, forming a cloudy solution. The solution is heated to 90° C. and mainained at this temperature under stirring condition for three hours. Subsequently, the pH of the solution is neutralized by addition of a water solution of sulphuric acid. Afterwards, 10% w/w of CMC and 5% w/w of glyoxal compared to the weight of PVA are added to solution. The solution is then diluted with water to afford a final solid content of 8% w/w. Finally, the solution is transfered to the coating apparatus for the coating step.

Example 3Silicone Anchorage of Low Temperature Curing (LTC) Silicone Systems

Standard glassine (STD) and the glassine produced by the methods reported in examples 1 (EX1) and 2 (EX2) have been siliconized with LTC silicones. The silicone anchorage results have been compared. In order to assess the silicone anchorage, a standard test called rub-off test has been performed; this test is an abrasion test in which a sample of siliconized paper, pressed under a weight, is dragged on an abrasive textile. The silicone layer at the surface of the sample can be removed by the rubbing. By measuring the amout of silicone onto the samples before and after the rubb-off test, it is possible to obtain a percentage of silicone that remains on the samples. The rub-off percentage 0% indicates that all the silicone has been removed from the sample, very poor adhesion; the rubb-off percentage 100% indicates that all the silicone remained on the sample, the adhesion is ideal. For the release application, the rub-off value of 75% is commonly considered as the bottom limit for silicone ancohorage. The following silicone formulation has been used in this example:

LTC silicone formulation bath:

Polymer: D920 (from Wacker)—18.07 g

Cross-linking agent: XV 525 (from Wacker)—1.43 g

Catalyst: CO5 (i.e.: Platinum based from Wacker)—2.14 g

Deposit: 0.9 g/m²

Cross-linking for 30 seconds at 80° C. in a ventilated drying kiln

Table 1 shows that STD has a rub-off value of 18% (very poor adhesion of the silicone), whereas EX1 and EX2 have respectively rub-off values of 96% and 97% (both samples have very good adhesion properties for LTC silicone systems). So, in the case of standard glassine the LTC silicone cannot be used due to the poor adhesion of the silicone system to the substrate; on the contrary, LTC silicone systems can be used on glassine produced by the methods reported in the present invention.

TABLE 1

Sample	STD	EX1	EX2

Rub-off value	18%	96%	97%

Example 4Silicone Anchorage Dependence on the Amount of Catalyst (i.e.: Platinum) in the Silicone Formulation

For thermal cured silicone systems used in release industry, the catalyst used is an organometallic compound of platinum. Due to the high price of platinum, there is a strong interest in reducing its amount in the silicone formulation. The first problem observed when a reduced amount of catalyst is used is a poor anchorage of the silicone to the substrate.

Standard glassine (STD) and the glassine produced by the methods reported in examples 1 (EX1) and 2 (EX2) have been siliconized with a standard silicone formulation by using two different amounts of catalyst in the silicone formulation, and the silicone anchorage on different substrates has been tested. In order to evaluate the silicone anchorage, the rub-off test (described in example 3) has been performed. For the tests the following silicone formulations have been used:

Standard silicone formulation bath:

Polymer: 11367 (from Bluestar)—50 g

Cross-linking agent: 12031 (from Bluestar)—2.9 g

Catalyst (60 ppm Platinum): 12070 (from Bluestar)—1.56 g; or (30 ppm Platinum): 12070-0.78 g

Deposit: 0.9 g/m²

Cross-linking for 10 seconds at 160° C. in ventilated drying kiln

As it is possible to observe in table 2, an satisfactory rate of silicone anchorage is obtained for all samples when the silicone formulation contains 60 ppm of platinum. On the contrary, when the amount of platinum is decreased to 30 ppm, the silicone anchorage of samples EX1 and EX2 remains very good but the anchorage of STD is poor.

TABLE 2

STD	EX1	EX2

Rub-off	90%	95%	98%
(60 ppm of Platinum)
Rub-off	54%	91%	93%
(30 ppm of Platinum)